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[31.30.173.16]) by smtp.gmail.com with ESMTPSA id w12-20020a05600c474c00b003f07ef4e3e0sm10730643wmo.0.2023.05.11.00.44.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 11 May 2023 00:44:40 -0700 (PDT) Date: Thu, 11 May 2023 09:44:39 +0200 From: Andrew Jones To: zhangfei Cc: linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, aou@eecs.berkeley.edu, palmer@dabbelt.com, paul.walmsley@sifive.com, conor.dooley@microchip.com, zhangfei@nj.iscas.ac.cn Subject: Re: [PATCH v2 0/2] RISC-V: Optimize memset for data sizes less than 16 bytes Message-ID: <20230511-75718c538818fb3e1d924f9a@orel> References: <20230511012604.3222-1-zhang_fei_0403@163.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230511012604.3222-1-zhang_fei_0403@163.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 11, 2023 at 09:26:04AM +0800, zhangfei wrote: > From: zhangfei > > At present, the implementation of the memset function uses byte by byte storage > when processing tail data or when the initial data size is less than 16 bytes. > This approach is not efficient. Therefore, I filled head and tail with minimal > branching. Each conditional ensures that all the subsequently used offsets are > well-defined and in the dest region. Although this approach may result in > redundant storage, compared to byte by byte storage, it allows storage instructions > to be executed in parallel, reduces the number of jumps, and ultimately achieves > performance improvement. > > I used the code linked below for performance testing and commented on the memset > that calls the arm architecture in the code to ensure it runs properly on the > risc-v platform. > > [1] https://github.com/ARM-software/optimized-routines/blob/master/string/bench/memset.c#L53 > > The testing platform selected RISC-V SiFive U74.The test data is as follows: > > Before optimization > --------------------- > Random memset (bytes/ns): > memset_call 32K:0.45 64K:0.35 128K:0.30 256K:0.28 512K:0.27 1024K:0.25 avg 0.30 > > Medium memset (bytes/ns): > memset_call 8B:0.18 16B:0.48 32B:0.91 64B:1.63 128B:2.71 256B:4.40 512B:5.67 > Large memset (bytes/ns): > memset_call 1K:6.62 2K:7.02 4K:7.46 8K:7.70 16K:7.82 32K:7.63 64K:1.40 > > After optimization > --------------------- > Random memset bytes/ns): > memset_call 32K:0.46 64K:0.35 128K:0.30 256K:0.28 512K:0.27 1024K:0.25 avg 0.31 > Medium memset (bytes/ns ) > memset_call 8B:0.27 16B:0.48 32B:0.91 64B:1.64 128B:2.71 256B:4.40 512B:5.67 > Large memset (bytes/ns): > memset_call 1K:6.62 2K:7.02 4K:7.47 8K:7.71 16K:7.83 32K:7.63 64K:1.40 > > From the results, it can be seen that memset has significantly improved its performance with > a data volume of around 8B, from 0.18 bytes/ns to 0.27 bytes/ns. > > The previous work was as follows: > 1. "[PATCH] riscv: Optimize memset" > 6d1cbe2e.3c31d.187eb14d990.Coremail.zhangfei@nj.iscas.ac.cn Cover letters should have a changelog, in this case a couple phrases stating what's different in v2 vs. v1. Thanks, drew > > Thanks, > Fei Zhang > > Andrew Jones (1): > RISC-V: lib: Improve memset assembler formatting > > arch/riscv/lib/memset.S | 143 ++++++++++++++++++++-------------------- > 1 file changed, 72 insertions(+), 71 deletions(-) > > zhangfei (1): > RISC-V: lib: Optimize memset performance > > arch/riscv/lib/memset.S | 40 +++++++++++++++++++++++++++++++++++++--- > 1 file changed, 37 insertions(+), 3 deletions(-) >